With mixed results, the popular author of such zany fare as My Teacher Flunked the Planet here tries his hand at historical romance. In 1853, 16-year-old Fortune Plunkett is leading her late father's six-person itinerant acting troupe westward in hopes of building a permanent theater in San Francisco. Along the way, in a sleepy Missouri town, the group picks up another player, Jamie, a handsome young fellow who causes blushes to creep up Fortune's cheeks. As their wagon rolls along-often, unfortunately, at a snail's pace-the spunky heroine finds herself torn between her growing affection for Jamie and her long-standing attraction to another actor in her group. Before reaching their destination, the players endure some harrowing, convincingly relayed moments (their wagon comes very close to falling off a cliff with one of the actors trapped inside; Fortune is carried downriver by a sudden flood; and cholera ravages her companions). But even more potentially devastating to Fortune is the misunderstanding that prompts Jamie's departure. Not to worry: a joyous conclusion awaits readers who hang on. These are less apt to be youngsters, however, than hardcore genre fans who don't mind tame romance and megadoses of melodrama. Ages 10-up. (Sept.)